This invention relates to a communication processing system having a multiple bus input structure for the transmission of differing data types.
In communication systems the station, or port, access circuits typically receive information which must be processed by a system resource. In some situations this data must be transferred to a high speed peripheral, such as a disk, and in some cases the information must be transferred to another port access circuit. For voice data, an efficient transfer medium is a time division bus where time slots are assigned for the duration of a call. For bursty, or high speed, data an efficient transfer medium is a packet-switched bus. Thus, an attempt to interface the access circuits with one or the other of the bus types results in a compromise of efficiency with a resultant reduction in system capability.
One solution to this problem would be to use a voice interface circuit between voice stations with a time division bus and to use a data interface circuit between data terminals with a packet-switched bus. Such an arrangement solves the basic problem but introduces other undesirable limitations. For example, the typical arrangement for using line circuits is to have the circuits plug into the back plane wiring of a board carrier or housing. Thus, following the above example, it would be necessary to dedicate specific board locations on the carrier to each type of bus and to only use the proper line card for interfacing each bus. This arrangement requires separate inventories of line cards and specific knowledge of which physical spaces each type of line card is adapted to use.
In such an arrangement another concern is the pre-engineering that would be required so that there will be enough available physical locations for each board type. Accordingly, systems which are designed primarily for voice would have more available time division positions than packet-switched positions. In such situations if the system migrates toward data terminals it may become necessary to restructure the physical layout to accommodate the necessary interface circuits. This restructuring is costly and inefficient. Accordingly, a need exists for a bus structure which will easily accommodate the various transmission requirements at all positions.